1. Field of the Invention.
The invention, in general, relates to devices for detecting the presence of fluids, such as leaking pollutants, and more particularly, a detector which provides an output that can produce complete status records using relatively inexpensive recording devices.
2. Description of the Prior Art.
Contamination of the environment, such as ground water, by various liquid pollutants, such as gasoline, has become a significant problem in recent years and a number of practical devices for detecting pollutants have been developed. See for example, U.S. Pat. No. 4,116,045 on an invention of Bronson M. Potter and U.S. Pat. No. 4,221,125 on an invention of John N. Oliver and Louis M. Sandler. Recording of the output of such detectors has been found to be useful for controlling pollution and, in some cases, has been made necessary by law. Since in some industries and businesses the sources of pollutants can be multitudious, it would be highly desirable that fluids detectors for the sensing of pollutants provide a output that can be utilized by relatively inexpensive recording devices.
U.S. Pat. No. 4,116,045, referred to above, provides as an output an alarm or a gauge that responds to varying current levels. The output disclosed in U.S. Pat. No. 4,221,125, is a voltage which can vary over a range and which activates a visual or audible indicator. In another prior art device which is based on a microprocessor, the output is provided in the form of discrete voltage levels, i.e. an output of one volt indicates the presence of a polar fluid such as water, an output of two volts indicates the presence of a non-polar fluid such as oil, and an output of three volts indicates the presence of a dry well. Such an output lends itself more readily to the creation of a record of the output, however, the microprocessor based device is relatively expensive. Further, for a complete record of the status of all probes, multiple parallel channels must be recorded simultaneously.